Crash Attenuation System for Aircraft

ABSTRACT

A crash attenuation system for an aircraft, the system having an airbag carried by the aircraft and inflatable generally adjacent an exterior of the aircraft. The airbag has at least one vent for releasing gas from the interior of the airbag. A gas source is in fluid communication with the interior of the airbag for inflating the airbag with gas generated provided by the gas source. A vent valve is provided for controlling a flow of gas through each vent, each vent valve being selectively configurable between an open state, in which gas can pass through the associated vent from the interior of the airbag, and a closed state, in which gas is retained within the interior of the airbag. The gas source is provided for at least partially re-inflating the airbag after venting of gas through the at least one vent.

BACKGROUND

1. Technical Field

The system of the present application relates generally to crashattenuation systems and specifically to crash attenuation systems foruse in aircraft.

2. Description of the Prior Art

Currently internal airbags are used in the automotive industry withinthe occupied volume to mitigate occupant injuries. Similarly, externalairbags have been used to attenuate decelerative loads to air and spacevehicles, such as escape modules, upon contact with the ground or water.Examples include the NASA Mars Rovers and the crew module of the GeneralDynamics/Grumman F-111.

During impact, the gas in the airbag must be vented to prevent gaspressurization and subsequent re-expansion, which may cause the occupantto accelerate backward. This effect is commonly known as rebound. Inaddition, the gas may be vented to prevent over-pressurization, whichcan cause failure of the airbag. Venting may be accomplished, forexample, through discrete vents or through a porous membrane that formsat least a portion of the skin of the airbag. Some types of airbags mayalso be used for flotation devices when a crash occurs in water.

Although great strides have been made in the area of aircraft flotationsystems, many short comings remain.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the system of the presentapplication, including its features and advantages, reference is nowmade to the detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is an oblique view of an aircraft incorporating a crashattenuation system according to the present application;

FIG. 2 is an enlarged, oblique view of an airbag portion of the crashattenuation system of FIG. 1;

FIG. 3 is a cross-section view of a valve portion of the airbag of FIG.2, the valve being shown in an open configuration;

FIG. 4 is a cross-section view of a valve portion of the airbag of FIG.2, the valve being shown in a closed configuration;

FIG. 5 is a side view of a portion of the helicopter of FIG. 1 prior toa crash on land;

FIG. 6 is a side view of a portion of the helicopter of FIG. 1subsequent to a crash on land;

FIG. 7 is a side view of a portion of the helicopter of FIG. 1 prior toa crash on water;

FIG. 8 is a side view of a portion of the helicopter of FIG. 1subsequent to a crash on water; and

FIG. 9 is a side view of a portion of the helicopter of FIG. 1subsequent to a crash on water and after re-inflation of the airbag.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There is a need for an airbag crash attenuation system for aircraft thatincludes automatic post-crash re-inflation in water, allowing for use ofthe airbag as a flotation device for the aircraft.

Therefore, it is an object of the present application to provide anairbag crash attenuation system for aircraft that includes automaticpost-crash re-inflation in water, allowing for use of the airbag as aflotation device for the aircraft.

A crash attenuation system for an aircraft, the system having an airbagcarried by the aircraft and inflatable generally adjacent an exterior ofthe aircraft. The airbag has at least one vent for releasing gas fromthe interior of the airbag. A first gas generator is in fluidcommunication with the interior of the airbag for inflating the airbagwith gas generated when the first gas generator is operated. A ventvalve is provided for controlling a flow of gas through each vent, eachvent valve being selectively configurable between an open state, inwhich gas can pass through the associated vent from the interior of theairbag, and a closed state, in which gas is retained within the interiorof the airbag. A second gas generator is provided for at least partiallyre-inflating the airbag after venting of gas through the at least onevent.

The system of the present application provides for an inflatable crashattenuation system for aircraft. The system comprises an airbag that isinflated prior to impact and vented during impact, but also includes theability to re-inflate for use as a post-crash flotation device. Thesystem of the present application may be used on all models of aircraft,for example, helicopter, fixed wing aircraft, and other aircraft, and inparticular those that are rotorcraft. The system of the presentapplication improves on the prior art by providing automatic control ofthe venting valves and providing for post-crash re-inflation. The systemof the present application may actually reduce the loads in an airframestructure needed to support large mass components (such as an engineand/or transmission), allowing for construction of lighter-weightairframe structures, which can offset the additional weight of the crashattenuation system.

FIG. 1 shows a helicopter 11 incorporating the crash attenuation systemaccording to the present application. Helicopter 11 comprises a fuselage13 and a tail boom 15. A rotor 17 provides lift and propulsive forcesfor flight of helicopter 11. A pilot sits in a cockpit 19 in a forwardportion of fuselage 13, and a landing skid 21 extends from a lowerportion of fuselage 13 for supporting helicopter 11 on a rigid surface,such as the ground.

A problem with rotor 17 or the drive system for rotor 17 may necessitatea descent from altitude at a higher rate of speed than is desirable. Ifthe rate is an excessively high value at impact with the ground orwater, the occupants of helicopter 11 may be injured and helicopter 11may be severely damaged by the decelerative forces exerted on helicopter11. To reduce these forces, inflatable, non-porous airbags 23, 25 areinstalled under fuselage 13. Though not shown in the drawings, airbags23, 25 are stored in an uninflated condition and are inflated under thecontrol of a crash attenuation control system (described below).

FIG. 2 is an enlarged view of airbag 23, which has a non-porous bladder27 and a plurality of discrete vents 29. Airbag 23 is shown in thefigure, but it should be noted that airbags 23, 25 have generallyidentical configurations. Vents 29 communicate the interior of bladder27, allowing for gas within airbag 23 to be vented. In the embodimentshown, vents 29 are open to the ambient air, though vents may beconnected to a closed volume, such as another airbag or an accumulator(not shown).

Referring to FIGS. 3 and 4, each vent 29 has a vent valve 31 forcontrolling the flow of gas through vent 29. Vent 29 and vent valve 31together form a vent passage 33 for channeling gas flowing out of airbag23. Each vent valve 31 is sealingly mounted in bladder 27 to prevent theleakage of gas around vent 31, which forces venting gas to flow throughpassage 33. A vent plate 35 is configured to be moveable between an openposition and a closed position. FIG. 3 shows vent plate 35 in the openposition, or open state, in which gas is allowed to flow through passage33 from within bladder 27. FIG. 4 shows vent plate 35 in the closedposition, or closed state, in which gas is prevented from flowing out ofbladder 27 into passage 33. Though shown as a sliding valve, it will beunderstood by one skilled in the art that vent valves 31 mayalternatively be other suitable types of valves. Control of vent valves31 may be accomplished though any number of means, including, forexample, electrorheological means.

FIGS. 5 through 9 show airbag 23 mounted to a lower portion of fuselage13 and show additional components of the crash attenuation systemaccording to the present application. A computer-based control system37, which is shown mounted within fuselage 13, is provided forcontrolling the operation of components associated with airbags 23, 25.In one embodiment, each airbag 23, 25 has a first gas source, such asgas generator 39, for initial inflation of the associated airbag 23, 25and a secondary gas source, such as compressed gas tank 41, forpost-crash re-inflation of airbag 23, 25. Each gas source may be ofvarious types, such as gas-generating chemical devices or compressedair, for providing gas for inflating airbags 23, 25. In anotherembodiment, the first gas source and the second gas source are actuallya single gas source. In such an embodiment, compressed gas tank 41, gasgenerator 39, or another type of gas source, can provide initialinflation of airbag 23, 25, as well as post-crash re-inflation of airbag23, 25. In addition, the system of the present application preferablyhas at least one sensor 43 for detecting rate of descent and/or groundproximity. Airbags 23, 25 also preferably have a water-detection system,which may have sensors 45 mounted on fuselage 13 for detecting a crashin water. Gas generator 39, compressed gas tank 41, vent valves 31, andsensors 43, 45 are connected to control system 37 through data and/orpower cables 47, allowing control system 37 to communicate with,monitor, and control the operation of these attached components. Inaddition, control system 37 may be connected to a flight computer orother system for allowing the pilot to control operation of the crashattenuation system. For example, the pilot may be provided means todisarm the system when the aircraft has safely landed.

FIGS. 5 through 9 illustrate operation of the crash attenuation system,with FIGS. 5 and 6 showing use during a crash onto a rigid surface, suchas the ground, and FIGS. 7 through 9 showing use during a crash intowater. Only airbag 23 is shown, though the operation of airbag 25 isidentical to that of airbag 23.

In operation, if an impending crash is sensed by sensor 43, for example,by excessive oncoming rate of the ground within a certain attituderange, control system 37 triggers primary gas generators 39 to inflateairbags 23, 25 at the appropriate time to allow full inflation just asairbags 23, 25 contact the impact surface (ground or water).

FIG. 5 shows an impending crash onto ground 49. Primary gas generator 39has already been triggered, and bladder 27 of airbag 23 is inflated justprior to contact with ground 49. FIG. 6 shows the effect on airbag 23during the impact, in which gas in bladder 27 is vented through vents 29to dissipate the gas pressure for minimizing the structural loading infuselage 13 due to the crash. To allow for gas to escape through vents29, vent valves 31 (described above) are commanded by control system 37to switch from being closed to being at least partially open. The amountby which vent valves 31 are opened at impact will be determined bycontrol system 37 based upon selected factors, which may include, forexample, the rate of descent and the weight of the aircraft.

FIG. 7 shows an impending crash onto water 51. Primary gas generator 39has already been triggered, and bladder 27 of airbag 23 is inflated justprior to contact with water 51. FIG. 8 shows the effect on airbag 23during the impact, in which gas in bladder 27 is vented through vents 29to dissipate the gas pressure for minimizing the structural loading infuselage 13 due to the crash. To allow for gas to escape through vents29, vent valves 31 (described above) are commanded by control system 37to switch from being closed to being at least partially open. Ifwater-detection sensors 45 detect water, control system 37 commands ventvalves 31 to close and then commands compressed gas tank 41 to releasegas into bladder 27 to at least partially re-inflate airbag 23. Thisallows airbags 23, 25 to release most or all of the gas provided byprimary gas generator 39 during the crash and also act as post-crashflotation devices, providing buoyancy to helicopter 11. The use ofcompressed gas allows for faster re-inflation, which is important toprevent further submersion of the aircraft.

It should be noted that having airbags 23, 25 deploy in centralpositions beneath an aircraft may lead to instability in water, whereinthe aircraft may be top-heavy and lean or turn over in water. Additionalbuoyant devices, such as airbags, may be used to prevent upset of theaircraft by spacing them from airbags 23, 25. For example, outriggerairbags may be deployed on landing skid 21 on helicopter 11.

The system of the present application provides the following advantages:(1) the combination of an inflatable crash attenuator system for crashload attenuation with a post-crash flotation system; (2) the use ofnon-porous airbag fabric with discrete venting nozzles that vent to theambient outside of the occupied zone; (3) the venting nozzle may be anactively controlled valve to minimize variability due to groundweight-center of gravity (GW-CG) changes, impact velocities, impactsurface compliance, and impact attitudes; and (4) the use of anautomatic valve as the venting nozzle that automatically closes uponcontact with water.

While the system of the present application has been described withreference to at least one illustrative embodiment, this description isnot intended to be construed in a limiting sense. Various modificationsand combinations of the illustrative embodiments, as well as otherembodiments of the system, will be apparent to persons skilled in theart upon reference to the description.

1. A crash attenuation system for an aircraft, the system comprising: anairbag carried by the aircraft and inflatable generally adjacent an to aposition exterior of the aircraft, the airbag having at least one ventfor releasing gas from the interior of the airbag for crash attenuation;a gas source in fluid communication with the interior of the airbag forinflating the airbag to the position exterior of the aircraft with gasprovided by the gas source; a vent valve for controlling a flow of gasthrough each of the at least one vent, each vent valve being selectivelyconfigurable between an open state, in which gas can pass through theassociated vent from the interior of the airbag, and a closed state, inwhich gas is retained within the interior of the airbag; and wherein thegas source is in fluid communication with the interior of the airbag forat least partially re-inflating the airbag with gas provided by the gassource after venting of gas through the at least one vent.
 2. The crashattenuation system according to claim 1, wherein the gas source is a gasgenerator.
 3. The crash attenuation system according to claim 1, whereinthe gas source is a compressed gas tank.
 4. The crash attenuation systemaccording to claim 1, further comprising: a water-detection system fordetecting the presence of water.
 5. The crash attenuation systemaccording to claim 1, further comprising: a water-detection system fordetecting the presence of water; wherein when the water-detection systemdetects water, each vent valve is switched to the closed state, and thegas source is used to at least partially re-inflate the airbag.
 6. Acrash attenuation system for an aircraft, the system comprising: anairbag carried by the aircraft and inflatable generally adjacent an to aposition exterior of the aircraft, the airbag having a vent configuredto release gas from the interior of the airbag for crash attenuation; agas source in fluid communication with the interior of the airbag, thegas source configured to inflate the airbag to the position exterior ofthe aircraft with gas provided by the gas source; a vent valveconfigured to control a flow of gas through the vent, the vent valvebeing selectively configurable between an open state, in which gas canpass through the vent from the interior of the airbag, and a closedstate, in which gas is retained within the interior of the airbag; awater-detection system for detecting the presence of water; wherein thegas source is in fluid communication with the interior of the airbag forat least partially re-inflating the airbag with gas provided by the gassource.
 7. The crash attenuation system according to claim 6, whereinthe gas source is a gas generator.
 8. The crash attenuation systemaccording to claim 6, wherein the gas source comprises compressed gas.9. The crash attenuation system according to claim 6, furthercomprising: wherein the water-detection system is configured to switchthe vent valve to the closed state upon detection of water.
 10. Thecrash attenuation system according to claim 6, wherein thewater-detection system is configured to direct the gas source to atleast partially re-inflate the airbag upon detection of water.
 11. Amethod of operating a crash attenuation system in an aircraft,comprising: inflating an airbag with a gas source that is in fluidcommunication with the interior of the airbag, the airbag being inflatedto an exterior of the aircraft; venting the airbag by releasing gasthrough a vent from the interior of the airbag, thereby providing crashattenuation to the aircraft; closing a vent valve that is associatedwith the vent; re-inflating the airbag with the gas source.
 12. Themethod according to claim 11, further comprising: sensing a presence ofwater with a water-detection system.
 13. The method according to claim11, wherein the gas source is a gas generator.
 14. The method accordingto claim 11, wherein the gas source is a compressed gas tank.
 15. Themethod according to claim 11, wherein the gas source comprises multiplegas sources.
 16. The method according to claim 11, wherein the step ofclosing the vent valve includes actuating a sliding a moveable ventplate into a closed position.
 17. The method according to claim 11,wherein the step of inflating the airbag is performed by acomputer-based control system.
 18. The method according to claim 11,further comprising: detecting an impending crash with a sensor.
 19. Themethod according to claim 11, wherein the step of inflating the airbagwith the gas source occurs just prior to impact of the aircraft with acrash surface.
 20. The method according to claim 11, further comprising:deploying at least one outrigger airbag to provide flotational stabilityto the aircraft.